Besides those who came on business there were gallants dressed in fashionable finery, so that it was worth the tailor's while to stand behind a pillar and fill his table-books with notes.

It was in these circumstances that he dictated to his servant, a tailor's apprentice, who was absolutely devoid of mathematical knowledge, his Anleitung zur Algebra (1770), a work which, though purely elementary, displays the mathematical genius of its author, and is still reckoned one of the best works of its class.